The title bar should be the same size as any other system window on your machine. For example compare it to the text in the title-bar of Internet Explorer. If it is not the same, there are several possibilities:
1. You have changed the default Windows Display settings. The default screen magnification setting is set to "Smaller - 100% (default)". Because you did not mention the exact Windows version, the terminology may differ slightly on newer Windows versions. This was from Win7.
2. You have changed the Forms Font and Icon Mapping setting; default.fontMap.defaultSize The default should be 900.
3. The applet parameter; clientDPI should be unset or set to 96.
If you have altered any of the above, this likely is causing your issue.
Regarding the background color of your forms, if you have not hardcoded a Background color you can change the background color at runtime by changing the colorScheme applet parameter. If you don't like one of the nine Oracle provides, you can create your own using the customColorScheme applet parameter. Details about how to do this are in the Forms Deployment Guide and the Forms New Features guide. Note that the New Features Guide assumes you are using the latest version (18.104.22.168 in this case) so some features mentioned in that doc may not be available to you if you are using an older release.
Forms 22.214.171.124 Deployment Guide: